3I/Atlas is the interstellar comet that recently disappeared behind the sun. It has now reappeared, but sans tail, "which would eliminate the conventional explanation for the surprising 'non-gravitational acceleration' it exhibited last week," reports the New York Post. "Photographs taken by the R. Naves Observatory in Spain on Nov. 5, showed no sign of a tail of debris which was expected to be shooting off behind the object as it encountered the force of the sun," according to the article.
Discussing these images, Harvard astrophysicist Avi Loeb comments:
The new image does not show evidence for a dust tail pointing away from the Sun, as expected from massive evaporation of a natural comet near perihelion. This is surprising in view of NASA’s JPL report here of a non-gravitational acceleration for 3I/ATLAS. Based on momentum conservation (as discussed here), I derived here that the mass fraction lost during the perihelion passage of 3I/ATLAS is larger than 13% in case it is a natural comet. This should have resulted in a massive coma with dust and gas that would have been pushed by the solar radiation pressure and the solar wind to the shape of a typical cometary tail pointing away from the Sun.
He acknowledges that it is possible we aren't seeing the tale because we are looking at the comet almost head on. "However," he points out, "this was also the perspective of the Hubble Space Telescope when it imaged the anti-tail from 3I/ATLAS towards the Sun at an angle of 10 degrees on July 21, 2025 (see discussion here). Nevertheless, the anti-tail was evident in the Hubble image as an elongation by a factor of 2 in the sunward direction from 3I/ATLAS."
More recent photographs from November 8, however, "show at least 7 distinct jets, some of which are anti-tails in the sunward direction" according to Loeb. "Is the network of jets associated with pockets of ice on the surface of a natural cometary nucleus," he asks, "or are they coming from a set of jet thrusters used for navigation of a spacecraft? We do not know."
More: "No Clear Cometary Tail in Post-Perihelion Images of 3I/ATLAS"--Avi Loeb. Discussing 10 anomalous traits or behaviors of the comet.
It's almost certainly natural. An odd thing, but natural.
ReplyDeleteAssuredly, but its fun to wonder.
DeleteAnd now they're finally seeing some hydrogen and oxygen (specifically HO ions), so the guys over at TheDebrief are giving the usual assurances that our standard explanation of comets is correct.
ReplyDeleteIt's gonna be fun when the physicists give up on dirty ice the same way they gave up on polar aurora made from sunlight and ice crystals.